Research and development have been made on display panels (hereinafter simply called “charged particle migration type display panels”) which use a charged particle migration system as an image display device, such as a personal digital assistant and electronic paper. For example, a charged particle migration type display panel with an active-matrix structure is configured to have a transparent substrate to which a common electrode is mounted, a back substrate on which a plurality of pixel electrodes are mounted, and partitions disposed between the transparent substrate and the back substrate, and have charged particles of dark color like black, and charged particles of light color like white, enclosed in individual cells partitioned by the transparent substrate, the back substrate and the partitions. As a predetermined voltage is applied to individual pixel electrodes to generate an electric field between the back substrate and the transparent substrate, the dark-colored or light-colored charged particles are migrated to the transparent substrate side to display black, white, or gray.
Such a charged particle migration type display panel has a problem such that since the partitions made of a transparent (in practice yellowish brown-colored) material are seen as a white-colored lattice pattern when in black display, the contrast ratio of the white display which has the maximum luminance to the black display which has the minimum luminance is deteriorated. In this respect, a charged particle migration type display panel provided with means for concealing the lattice pattern of the partitions has been proposed.
There is known a charged particle migration type display panel configured so that a black matrix layer (black pattern) corresponding to partitions is provided on the inner surface of the transparent substrate or the back substrate. Further, there is also known a charged particle migration type display panel configured to have partitions formed of an opaque material of white, gray or the like, and have a black matrix layer formed on the top surfaces of the partitions.
However, the former charged particle migration type display panel mentioned above is configured to cover only the end faces of partitions with a black matrix layer, so that while the end faces of the partitions can be unseen from the front side of the transparent substrate, the transparent side faces of the partitions are visible from the oblique direction to the transparent substrate, thereby degrading the contrast ratio.
In the latter charged particle migration type display panel mentioned above, however, a filler, a dye, or a paint is contained in the material for the partitions to make the partitions opaque. In the case where an ultraviolet curing resin is used as a material for the partitions, there is a problem that the lower the transmittancy becomes, the more difficult it becomes for light to pass through the ultraviolet curing resin, so that it is not possible to form the partitions of a desired pattern with a high accuracy. In the charged particle migration type display panel of the prior art, therefore, even if the partitions could be made white or gray, the partitions themselves could not be made into a black matrix with a dark color close to black. As a result, as in the above case, the transparent side faces of the partitions are visible from the oblique direction to the transparent substrate, thereby degrading the contrast ratio.